Preparation

For herb oil:
Whisk all ingredients in small
bowl. DO AHEAD: Can be made 4 days ahead.
Cover and chill. Bring to room temperature
and rewhisk before using.

For hash:
Preheat oven to 350°F. Cut
greens and stems off all beets; discard
stems. Coarsely chop enough beet greens
to measure 4 loosely packed cups. Bring
medium saucepan of salted water to boil.
Add greens and cook just until wilted, about
1 minute. Drain well. Set aside. Scrub beets;
place in 8x8x2-inch glass baking dish. Pour
half of herb oil over beets; sprinkle with salt
and pepper. Cover baking dish with foil and
roast beets until tender when pierced with
small sharp knife, about 1 hour. Remove
from oven and let beets stand until cool
enough to handle. Peel beets; cut into
1/2-inch pieces and reserve. DO AHEAD: Beet
greens and beets can be made 1 day ahead.
Cover separately and chill.

Increase oven temperature to 375°F.
Combine squash, potatoes, and yams in
large bowl. Add remaining herb oil and
toss to coat. Sprinkle generously with salt
and pepper. Spread vegetable mixture
evenly on large rimmed baking sheet. Roast
until vegetables are tender when pierced
with knife and lightly browned around
edges, stirring and turning vegetables
occasionally, about 50 minutes. DO AHEAD:
Can be made 2 hours ahead. Let stand
uncovered at room temperature. Rewarm
in 350°F oven until heated through, about
15 minutes.

Stir beets and beet greens into roasted
vegetables; dot with butter cubes and
continue to roast just until beets are
heated through, 5 to 10 minutes. Transfer
vegetable mixture to large bowl and serve.